Antarctic Blue Whale Set to Make Big Comeback

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After commercial whalers decimated their population during the
20th century, the Antarctic blue whale may be on the verge of a
comeback. The first genetic analysis of the whales has found a
surprisingly high level of diversity in the population.

"Fewer than 400 Antarctic blue whales were thought to have
survived when this population was protected from
commercial hunting in 1966," Angela Sremba, who performed the
research as part of her master's degree at Oregon State
University, said in a statement.

"The exploitation period, though intense, was brief in terms of
years, so the whales' long life span and overlapping generations
may have helped retain the diversity," Sremba said. "Some of the
Antarctic blue whales that survived the genetic bottleneck may
still be alive today."

Hunted populations

Since the International Whaling Commission banned commercial
hunting of the Antarctic blue whale (Balaenoptera musculus
intermedia) in 1966, the subspecies has rebounded and now
numbers around 2,200 individuals. The whales live in chilly
waters
around Antarctica and survive by eating tiny crustaceans
called krill. They are related to both the subspecies that lives
in the North Atlantic and Pacific oceans, called B. m.
musculus, and the pygmy species (B. m. brevicauda)
found in the Indian and South Pacific oceans.

"These animals are very long-lived — maybe 70 to 100 years — and
they can grow to a length of more than 100 feet [more than 30
meters] and weigh more than 330,000 pounds [150 kilograms],"
study researcher Scott Baker, associate director of the Marine
Mammal Institute at Oregon State University, said in a statement.
"There is a jawbone in a museum in South Africa that takes up
most of the lobby." [ Album:
The World's Biggest Beasts ]

The researchers analyzed the genetics of 215 Antarctic blue whale
tissue samples (from 166 individuals) collected between 1990 and
2009. They specifically examined certain genetic markers to see
how closely related these different individuals were, and found
they weren't as related as researchers would expect from a small
population — they had surprisingly high levels of genetic
diversity.

Some endangered wildlife populations, such as the
Florida panther, end up small and extremely inbred, which
means they have high levels of relatedness between two
individuals and low genetic diversity. These inbred populations
have trouble breeding, because detrimental genes become abundant
in the population, and this lowers their ability to have healthy
offspring.

The genetic study indicates that the whales have escaped the
inbred fate of the panther: Their numbers are small, but they
still have high genetic diversity and don't seem to suffer from
much inbreeding. That, Sremba said, may bode well for their
future recovery.

"This is a poorly understood
species of whales, despite its history of exploitation,"
Baker said. "Only now are we developing the technology to study
such a small number of whales spread across such a vast habitat."

The study is published online today, March 7, in the journal PLoS
ONE.

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